Thoracic gas compression during forced expiration is greater in men than women.

Elizabeth A Gideon,Dallin S Merrell,Troy J Cross,Brooke E Cayo,Aaron W Betts,Lauren E Hays,Catherine L Coriell,Joseph W Duke

doi:10.14814/phy2.14404

Elizabeth A Gideon, Dallin S Merrell + Show 6 more

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https://doi.org/10.14814/phy2.14404

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Abstract

Intrapleural pressure during a forced vital capacity (VC) maneuver is often in excess of that required to generate maximal expiratory airflow. This excess pressure compresses alveolar gas (i.e., thoracic gas compression [TGC]), resulting in underestimated forced expiratory flows (FEFs) at a given lung volume. It is unknown if TGC is influenced by sex; however, because men have larger lungs and stronger respiratory muscles, we hypothesized that men would have greater TGC. We examined TGC across the “effort‐dependent” region of VC in healthy young men (n = 11) and women (n = 12). Subjects performed VC maneuvers at varying efforts while airflow, volume, and esophageal pressure (POES) were measured. Quasistatic expiratory deflation curves were used to obtain lung recoil (PLUNG) and alveolar pressures (i.e., PALV = POES–PLUNG). The raw maximal expiratory flow–volume (MEFVraw) curve was obtained from the “maximum effort” VC maneuver. The TGC‐corrected curve was obtained by constructing a “maximal perimeter” curve from all VC efforts (MEFVcorr). TGC was examined via differences between curves in FEFs (∆FEF), area under the expiratory curves (∆AEX), and estimated compressed gas volume (∆VGC) across the VC range. Men displayed greater total ∆AEX (5.4 ± 2.0 vs. 2.0 ± 1.5 L2·s−1; p < .001). ∆FEF was greater in men at 25% of exhaled volume only (p < .05), whereas ∆VGC was systematically greater in men across the entire VC (main effect; p < .05). PALV was also greater in men throughout forced expiration (p < .01). Taken together, these findings demonstrate that men display more TGC, occurring early in forced expiration, likely due to greater expiratory pressures throughout the forced VC maneuver.

Highlights

The forced vital capacity (VC) maneuver provides substantive information about an individual’s respiratory health and function (Miller et al, 2005)
Examination of the change in spirometry parameters revealed that only the change in forced expiratory flows (FEFs) at 25% of VC was greater in men than in women when expressed in absolute units (p = .003) and as a percent of MEFVcorr (p = .01)
We observed that thoracic gas compression (TGC) was present in all subjects, regardless of sex

Summary

Introduction

The forced vital capacity (VC) maneuver provides substantive information about an individual’s respiratory health and function (Miller et al, 2005). | 2 of 11 individual must produce large, positive swings in intrapleural pressure (often approximated by esophageal pressure [POES] (Gillespie, Lai, & Hyatt, 1973; Hurewitz, Sidhu, Bergofsky, & Chanana, 1984; Hamid, Shannon, & Martin, 2005)) These pressures, are often far in excess of those required to generate maximum expiratory airflow (i.e., expiratory flow limitation) (Ingram & Schilder, 1966; Sharafkhaneh et al, 2007). These previous studies provided comments on intra-subject variability of TGC within their experimental groups; no study to date has deliberately examined how participant sex may affect the degree of TGC observed during forced VC maneuvers (Cross et al, 2018; Guenette et al, 2010; Sharafkhaneh et al, 2007)

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